1446341 - The XUL "tree" widget will be removed from mozilla-central

Reporter

Description

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6 years ago

As noted in bug 1446335, as part of the architectural efforts to remove XUL from mozilla-central, we are looking into deleting the "tree" widget entirely.

While this removal will not happen very soon, the eventual plan of record does not involve developing a replacement that provides the same user experience. Instead, each of the current uses of "tree" in mozilla-central will be evaluated independently and replaced with an alternative that works for the specific use case.

Keeping this in mind, I expect that Thunderbird and SeaMonkey will also have to develop alternatives for the portions of their user interface that depend on "tree", or adopt the technology into comm-central.

Jorg K (CEST = GMT+2)

Comment 1

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6 years ago

Thanks for the heads-up. I believe we've already looked into a replacement for the tree widget, but I'd have to find where that was done.

Jorg K (CEST = GMT+2)

Comment 2

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6 years ago

Found some stuff:
- Bug 1183812 comment #3
- https://mail.mozilla.org/pipermail/tb-planning/2017-March/005322.html

Ben Bucksch (:BenB)

Comment 3

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6 years ago

http://benbucksch.github.io/trex/fastlist-test.html

Ben Bucksch (:BenB)

Comment 4

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6 years ago

XUL <tree> is completely central to Thunderbird's UI. The XUL <tree> was originally implemented specifically for Thunderbird, and with the needs of Thunderbird in mind. The folder pane and the thread pane are XUL <tree>s, and the thread pane is the most prominent UI of Thunderbird.

It is highly complex and needs:
* Fast enough for up to 1 million entries
* tree: hierarchical entries with expander
* table: multiple columns, sortable, configurable
* the combination of tree and table at the same time
Without XUL <tree>, and without a suitable replacement that at the very minimum does all of that, Thunderbird will simply be dead.

@Everybody: To start, it would be good to compile a list of requirements that the new implementation needs. The above list is just the big picture, but there are many small requirements to be worked out.

This will not be trivial, and won't be done in a weekend. I've already looked, and there's nothing out there that even comes close. This is a 6-12 months project with full time staff, given that so much of Thunderbird hangs off it. We need a suitable replacement that meets all requirements of Thunderbird, *before* XUL <tree> is removed. Otherwise the project is dead.

@Paolo: I understand that this is just a placeholder and you don't have a timeline yet. But this needs a concerted effort to create a replacement, and is a large project on its own. If you want the Thunderbird project to handle this, we'd need 2 years of ahead warning time, and funds to create the replacement, and need to build a development team for it etc..

:Paolo Amadini

Reporter

Comment 5

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6 years ago

(In reply to Ben Bucksch (:BenB) from comment #4)
> @Everybody: To start, it would be good to compile a list of requirements
> that the new implementation needs.

I like the approach of taking a bird's eye view at the requirements of Thunderbird as an application, that is followed here and in the linked Thunderbird newsgroup post, and I would go even further in suggesting that a modern user interface for listing messages and threads could have different levels of similarities to the current list with the tiny expander icons and a single overarching scrollbar.

In the end, what this will look like in two to three years is a decision for the Thunderbird community to make, both from a code and interface design perspective.

> @Paolo: I understand that this is just a placeholder and you don't have a
> timeline yet. But this needs a concerted effort to create a replacement, and
> is a large project on its own. If you want the Thunderbird project to handle
> this, we'd need 2 years of ahead warning time, and funds to create the
> replacement, and need to build a development team for it etc..

It looks like the removal of the tree widget has worked as a good conversation starter, probably because it is demonstrably achievable and it does require some dedicated work to replace. However, as you noted in the newsgroup, this is just part of a bigger effort to remove XUL from mozilla-central. Just as an example, bug 1444468 is related to the removal of XUL overlay technology from the platform, which will happen much sooner. This recent thread lists other parts of XUL for which there is an action plan:

https://mail.mozilla.org/pipermail/firefox-dev/2018-March/006240.html

All the little fixes needed as a consequence will likely require more effort overall than a new interface for listing messages. The same long-term planning considerations for Thunderbird also apply to these changes, and I can only anticipate them becoming more pressing as the XUL removal project gains momentum.

Speaking of ahead warning time, my general consideration is that in all communications we've been quite explicit about the intent to remove XUL for quite some time now, and it doesn't certainly come as a surprise, although only more recently this idea started to be an effort concretely led by engineering. In fact, this is the best time to make a Thunderbird counterpart to these concrete engineering plans, and take decisions.

As an engineering choice, we already took the explicit direction of removing the XUL code from mozilla-central entirely, doing this incrementally as we remove features. Given this, I believe that adopting portions of the mozilla-central platform code in comm-central may be the solution to gain the lead time you mention here, and may work for the "tree" widget. This may take different forms, one of which is branching some or all of the top-level folders and maintaining vendor patches. Of course this is just a suggestion from the perspective of someone not deeply involved with comm-central development, and there may be different options available, which Thunderbird, SeaMonkey, and other projects based on mozilla-central can evaluate.

Ben Bucksch (:BenB)

Comment 6

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6 years ago

> Speaking of ahead warning time, my general consideration is that in all communications we've been
> quite explicit about the intent to remove XUL for quite some time now

I have been constantly - both outside the TB Council and from within - telling everybody that XUL will soon be gone. Every time, a discussion unfolds about how Mozilla has announced this since a decade, and that it's still years away. But despite all my efforts, nothing moves.

The lack of a clear, definite and reliable timeline is the very thing that has blocked Thunderbird's progress. We need to know: XUL overlay will be removed on March 2019, XUL tree on March 2020 etc., and we need you to stick to that time table. Without such a plan, we cannot act. From the time we have a concrete, definite reliable and official timeline on our hands, we need 2-3 years.

Thunderbird has a much larger UI surface than Firefox and relies very heavily on all facets of XUL. XUL overlays, on XUL <tree> and all features of XUL. We will need about 3 years to move away from XUL, and 18-24 months to move away from XUL <tree>, given how core it is to our user interface and also to the user experience.

Dave Townsend [:mossop]

Comment 7

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6 years ago

(In reply to Ben Bucksch (:BenB) from comment #6)
> > Speaking of ahead warning time, my general consideration is that in all communications we've been
> > quite explicit about the intent to remove XUL for quite some time now
> 
> I have been constantly - both outside the TB Council and from within -
> telling everybody that XUL will soon be gone. Every time, a discussion
> unfolds about how Mozilla has announced this since a decade, and that it's
> still years away. But despite all my efforts, nothing moves.
> 
> The lack of a clear, definite and reliable timeline is the very thing that
> has blocked Thunderbird's progress. We need to know: XUL overlay will be
> removed on March 2019, XUL tree on March 2020 etc., and we need you to stick
> to that time table. Without such a plan, we cannot act. From the time we
> have a concrete, definite reliable and official timeline on our hands, we
> need 2-3 years.

I doubt we can give you such an accurate timeline that far out. We certainly intend to give timelines wherever we can but as usual they are always affected by staffing changes etc. That's just the reality of software development.

> Thunderbird has a much larger UI surface than Firefox and relies very
> heavily on all facets of XUL. XUL overlays, on XUL <tree> and all features
> of XUL. We will need about 3 years to move away from XUL, and 18-24 months
> to move away from XUL <tree>, given how core it is to our user interface and
> also to the user experience.

Honestly I doubt you have that long. <tree> might be one of the later ones we remove since as you know there is no direct alternative and we have a bunch of uses in Firefox too, but if we're only finally removing the XUL code in three years time I think something will have gone very wrong.

Ben Bucksch (:BenB)

Comment 8

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6 years ago

> reality of software development

That's understood. Nonetheless, some planning and time tables are required. Esp. in a case like this where the removal of parts of XUL threatens the very existence of the Thunderbird project. Thunderbird has 25 million users, after all. They love Thunderbird as it is, which puts us TB developers in a very tough spot.

> but if we're only finally removing the XUL code in three years time I think something will have gone very wrong.

Given that some TB Council members think that the XUL removal is years out, we need some *definite* and concrete statements. I understand you, but most others simply don't believe such vague statements. The time table also has a large influence on the solution we choose. So, we really need more concrete information in order to act.

Dave Townsend [:mossop]

Comment 9

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6 years ago

(In reply to Ben Bucksch (:BenB) from comment #8)
> > reality of software development
> 
> That's understood. Nonetheless, some planning and time tables are required.
> Esp. in a case like this where the removal of parts of XUL threatens the
> very existence of the Thunderbird project. Thunderbird has 25 million users,
> after all. They love Thunderbird as it is, which puts us TB developers in a
> very tough spot.
> 
> > but if we're only finally removing the XUL code in three years time I think something will have gone very wrong.
> 
> Given that some TB Council members think that the XUL removal is years out,
> we need some *definite* and concrete statements. I understand you, but most
> others simply don't believe such vague statements. The time table also has a
> large influence on the solution we choose. So, we really need more concrete
> information in order to act.

We can come up with the broad strokes for when XUL might be completely gone from mozilla-central but the reality is that we will probably remove support for individual elements opportunistically along the way as we remove use of them in Firefox. We'll only understand the specifics of those as we come across them, maybe only being able to give weeks or less notice.

Ben Bucksch (:BenB)

Comment 10

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6 years ago

That doesn't leave Thunderbird much room to act.

Please coordinate with us.